The effect of ion beam treatment and subsequent annealing on Au/GaAs contacts

The effect of Xe++ and Ar+ ion beam treatment and subsequent annealing on the Au (55 nm)/n-GaAs system was studied using cross-sectional transmission electron microscopy. The maximum depth of observed defects caused by Xe++ ions (700 keV, 1×1014 ions/cm2) was about 400 nm from the interface in excellent agreement with the results of capacitance-voltage measurements. The formation of about 50-nm-thick polycrystalline region of GaAs was observed. The ion beam treatment resulted in the formation of defects (stacking faults, twins) down to a depth of 200 nm measured from the interface. Between 200 and 400 nm depth dislocation loops were formed. Amorphization has not been observed. The sharp Au/GaAs interface has been only slightly destroyed in the as-implanted sample. In contrast to pits in unirradiated samples, large flat grains of Au(Ga) solid solution grown into the highly damaged region of GaAs were found in the samples annealed at 450 °C after the ion beam treatment. The formation of a regrown GaAs covering layer was observed on the top of the reacted metallization. High dose implantation of Xe++ ions resulted in the formation of an amorphous GaAs layer with a thickness of about 750 nm. A phase transition caused by the ion beam was observed in this sample. During annealing at 400 °C the whole amorphous GaAs region recrystallized to single-crystal GaAs. Ion beam treatment with Ar+ ions (400 keV, 2×1014 ions/cm2) caused the formation of dislocation loops. In this case the growth of pits is similar to the case of simple annealing without bombardment.